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  <script>

    /* 
      递归(recursion)函数：
          1. 函数内部，自己调用自己
          2. 防止死循环
          3. 函数在栈里面执行，防止栈溢出

      循环的四要素：初始化条件; 变化条件; 判断条件; 执行逻辑     
    */

    let number = 1;
    function fn() {
      number++;
      console.log('富士山下');
      if (number == 6) {
        return;
      }

      fn();
    }

    fn();

  </script>
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